In the field of medicine in particular, the demands on an imaging system in terms of the image reproduction characteristic of said system, e.g. of a panel of a flat screen, are extremely high. The image reproduction characteristic indicates how an electrical image signal is converted into an optical signal, consisting of luminance and chrominance. It is desirable, for example, that the luminance increases in a perceptually equidistant manner as a function of a video input signal (a video level). Perceptually equidistant means that the human eye perceives the image e.g. at a video level of 50% of its maximum value as half as bright as the image at a 100% video level. In order to achieve this, measures are necessary to adjust the shape of a luminance characteristic curve to the sensitivity of the human eye.